(a) Field of the invention
The present invention relates to an automatic accompaniment apparatus for automatic bass chord (ABC) performances in or for an electronic musical instrument, and more particularly to an improvement of the automation accompaniment apparatus of the type designed to detect a chord type such as major, minor and so forth based on the state of key depression on the manual and pedal keyboards to thereby control the generation pattern of bass chord tones.
(b) Description of the prior art
In the past, as the automatic accompaniment apparatuses for automatic bass chord performances, there is known the apparatus arranged so that the root note and the type of the chords are designated on the manual keyboard, and along therewith a desired note is designated on the pedal keyboard, to thereby realize a bass chord performance (e.g. see U.S. Pat. No. 4,184,401). In this prior art apparatus, arrangement is provided so that the tones of a triad or a four-note chord, each containing the root note of the chord, are generated is the chord tones in accordance with a chord pattern corresponding to the designated chord type, whereas as a tone (bass root note) designated on the pedal keyboard and another tone (subordinate tone) of a predetermined interval (e.g. minor 3rd, perfect 5-th, etc.) relative to the bass root note are generated as the bass tones in accordance with the bass pattern corresponding to the designated chord type.
As another automatic accompaniment apparatus of the prior art, there is known the arrangement that the chord is detected based on the state of key depressions on both the manual and pedal keyboards, and that the note name designated on the pedal keyboard is utilized as the root note to thereby realize a bass chord performance.
In this latter prior art apparatus, chord tones are generated in the form of a triad or a four-note chord in accordance with the chord pattern corresponding to the detected chord type respectively containing a root note, whereas as the bass tone, there are generated a root note and its related subordinate notes in accordance with the bass pattern corresponding to the detected chord type.
In such an automatic accompaniment apparatus of the prior art as described above designed so that the root note of a chord and the type of this chord are designated on the manual keyboard and that an arbitrary note is designated on the pedal keyboard, it is possible to enjoy a bass progression rich in variation by designating, by the use of the pedal keyboard, a bass root note which differs in note name from the chord root note designated on the manual keyboard. However, the above-mentioned prior art apparatus is entailed by the inconvenience that, at the time of bass tone progression, there is generated bass tones which is discord relative to the chord tones which are produced. For example, let us here assume that C-major is designated on the manual keyboard and a bass root note B is designated on the pedal keyboard. Whereupon, a triad consisting of C-E-G is generated as the chord tones in accordance with the chord pattern for the major chord, and along therewith, the bass tones which consist of B and F.music-sharp. notes are generated in accordance with the bass pattern in the major mood, so that the F.music-sharp. bass tone is not in harmony with the chord tones of C-major.
On the other hand, in the automatic accompaniment apparatus described above which is designed so that the chord type is detected based on the state of key depressions on both the manual and pedal keyboards and that the note name designated on the pedal keyboard is utilized as the root note, the performer is unable to designate a bass root note which differs in note name from the root note of the chord, so that the apparatus is unable to realize the so-called "non-root-bass chord" performances.
Here, the term "non-root-bass chord performance" points to a performance such that, while generating a specific note as the bass tone, chord tones containing a root note which differs in note name from said specific bass tone are generated. For example, the non-root-bass chord "C.sub.7th /E" (C.sub.7 on E) generates a note E as the bass tone and also a four-note chord of C.sub.7th as the chord tones. Even when the player designates C, E, G and Bb on the manual keyboard while designating the note E on the pedal keyboard in order to make such a performance as mentioned above, the apparatus per se will play in such a way that the chord is performed with the chord pattern for the seventh using "E" as the root note, and that the bass is performed with the bass pattern for the seventh on the root note "E". Therefore, after all, the performance plunges into a bass chord performance for "E.sub.7th ".